In recent years, LED lighting devices for use in ordinary illumination or decoration have been provided with improved luminous efficiency of LEDs. Such LED lighting devices have an LED module with a plurality of LED elements surface-mounted at the leading end side of a housing and a translucent lens unit covering the module, and discharges outwardly radiation light from the LED elements. When the LED elements are raised in temperature to 90 degrees or more, their light power decreases or their life time becomes shorter. Accordingly, the preferred temperature of the LED elements is 50 degrees or less. In addition, a power circuit part for LEDs stored in the housing has a heat generator such as a capacitor, and it is known that, with abnormal temperature rise at the power circuit, the circuit may be deteriorated in operating reliability and life time.
Accordingly, conventional LED lighting devices are structured such that the housing has a metal heat dissipation part to prevent temperature rise at the LED elements and the power circuit, and to dissipate outwardly heat transferred from the LED elements and the power circuit. In particular, there has been suggested an LED lighting device in which a heat dissipation part has a heat sink formed by not an aluminum die-casting but a metal cylindrical main unit and a press-formed cooling fin part, and the LED lighting device is lightweight and excellent in heat dissipating property, and realizes significant reduction in manufacturing costs (refer to Patent Literature 1).
However, for example, if an LED lighting device is used instead of a mercury lamp to increase power output from a light source, heat generation also increases and hence it is difficult to cool down the light source naturally by contact with external air, which may result in deterioration of the elements. Accordingly, there has been suggested a structure in which heat from a light source and a housing is forcedly discharged using a forcing air flow generated by a fan motor (refer to Patent Literature 2, for example). However, according to the suggested forced cooling method, heat is discharged through an air flow path provided in the light source and thus dust and foreign objects are likely to enter the flow path. For example, the device may cause an accident such as firing if any flammable object contacts the light source, or the device may decrease in luminous efficiency or the like if dust or the like adheres to and accumulates on the internal surface of a lens unit.